WASHINGTON — The Supreme Court ruled this morning the Constitution's "right to keep and bear arms" applies nationwide as a restraint on the ability of the federal, state and local governments to substantially limit its reach.

In doing so, the justices, by a narrow 5-4 margin, signaled less severe restrictions could survive legal challenges.

Justice Samuel Alito, writing for the court, said the Second Amendment right "applies equally to the federal government and the states."

The court was split along familiar ideological lines, with five conservative-moderate justices in favor of gun rights and the four liberals, opposed.

Two years ago, the court declared the Second Amendment protects an individual's right to possess guns, at least for purposes of self-defense in the home.

That ruling applied only to federal laws. It struck down a ban on handguns and a trigger lock requirement for other guns in the District of Columbia, a federal city with a unique legal standing. At the same time, the court was careful not to cast doubt on other regulations of firearms here.

Gun rights proponents almost immediately filed a federal lawsuit challenging gun control laws in Chicago and its suburb of Oak Park, Ill, where handguns have been banned for nearly 30 years. The Brady Center to Prevent Gun Violence says those laws appear to be the last two remaining outright bans.

Lower federal courts upheld the two laws, noting that judges on those benches were bound by Supreme Court precedent and that it would be up to the high court justices to ultimately rule on the true reach of the Second Amendment.

The Supreme Court already has said that most of the guarantees in the Bill of Rights serve as a check on state and local, as well as federal, laws.